Internet DRAFT - draft-sivabalan-pce-disco-segment-routing
draft-sivabalan-pce-disco-segment-routing
Internet Engineering Task Force S. Sivabalan
Internet-Draft J. Medved
Intended status: Standards Track Cisco Systems, Inc.
Expires: February 01, 2014 July 31, 2013
IGP Extensions for Segment Routing Capable PCE Discovery
draft-sivabalan-pce-disco-segment-routing-00.txt
Abstract
When a PCE is a Label Switching Router (LSR) participating in
Interior Gateway Protocol (IGP), or a server participating in IGP,
its presence and path computation capabilities can be advertised
using IGP flooding. Such IGP extensions exist for OSPF and ISIS to
advertise several such capabilities. Segment Routing (SR) leverages
the source routing and tunneling pardigms in which a node steers a
packet through the network using segments. A segment can be an MPLS
label or IPv6 header with a new extension. In SR networks, a PCE can
be used to compute paths using SR PCEP extension. This document
specifies additional capability to advertise a PCE that supports the
new SR PCEP extension.
Status of This Memo
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This Internet-Draft will expire on February 01, 2014.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IGP Extensions for SR Capability . . . . . . . . . . . . . . 3
4. Backward Compatibility . . . . . . . . . . . . . . . . . . . 4
5. Management Considerations . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP),
which defines the communication between a Path Computation Client
(PCC) and a Path Control Element (PCE), or between PCE and PCE,
enabling computation of Multiprotocol Label Switching (MPLS) for
Traffic Engineering Label Switched Path (TE LSP) characteristics.
[I-D.ietf-pce-stateful-pce] specifies a set of extensions to PCEP to
enable stateful control of TE LSPs between and across PCEP sessions
in compliance with [RFC4657].
SR technology leverages the source routing and tunneling paradigms.
A node steers a packet through a controlled set of instructions,
called segments, by prepending the packet with an SR header. This
technology enables any head-end node to select any path without
relying on hop-by-hop signaling technique (e.g., LDP or RSVP-TE). It
depends only on segments that are advertised by IGPs. SR
architecture is described in [SR-ARCH]. A SR path can be derived
with an aid of a PCE. Extension to PCE Protocol (PCEP) to support SR
Traffic Engineering (SR-TE) path computation functionality is
specified in [SR-PCEP].
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When PCCs are LSRs participating in the IGP (OSPF or IS-IS), and PCEs
are either LSRs or servers also participating in the IGP, an
effective mechanism for PCE discovery within an IGP routing domain
consists of utilizing IGP advertisements. Such extension to OSPF and
IS-IS exists in [RFC5088] and [RFC5089], respectively.
Currently, the IGP PCE capability does not indicate whether the
advertised PCE is capabable of supporting SR PCEP extension specified
in [SR-PCEP]. Advertising such capability would facilitate a PCC to
learn about available SR capable PCEs. A PCC could listen to IGP
updates, or use other mechanisms that carry IGP information to
interested clients, such as BGP-LS ([I-D.ietf-idr-ls-distribution]).
This document extends the IGP capability advertisement mechanism to
include SR capability.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]
2. Terminology
The following terminology is used in this document:
IGP: Interior Gateway Protocol
IS-IS: Intermediate System to Intermediate System
LSR: Label Switching Router
OSPF: Open Shortest Path First
PCC: Path Computation Client
PCE: Path Computation Element
PCEP: Path Computation Element Protocol
SR: Segment Routing
SR-TE: Segment Routed Traffic Engineering
3. IGP Extensions for SR Capability
The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to advertise
PCE capabilities. It MAY be present within the PCED sub-TLV carried
by OSPF or IS-IS. [RFC5088] and [RFC5089] provide the description
and processing rules for this sub-TLV when carried within OSPF and
IS-IS respectively.
The PCE-CAP-FLAGS sub-TLV has the following format:
o TYPE: 5
o LENGTH: Multiple of 4
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o VALUE: This contains an array of units of 32 bit flags with the
most significant bit as 0. Each bit represents one PCE capability
PCE capability bits are defined in [RFC5088]. This document defines
new capability bits for the SR capable PCE as follows:
Bit Capability
13 Segment Routing PCE capability
4. Backward Compatibility
An LSR that does not support the new IGP PCE capability bits
specified in this document silently ignores those bits.
IGP extensions defined in this document do not introduce any new
interoperability issues.
5. Management Considerations
A configuration option may be provided for advertising and
withdrawing SR capability on a PCE.
6. Security Considerations
Security considerations described in [RFC5088] are applicable to
stateful PCE capabilities. No additional security measures are
required.
7. IANA Considerations
IANA is requested to allocate a new bit in "PCE Capability Flags"
registry for SR PCE capability as follows:
Bit Meaning Reference
13 SR PCE capability This document
Table 1
8. References
8.1. Normative References
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-02
(work in progress), February 2013.
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[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-03 (work in progress), March 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[SR-ARCH] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and M. Horneffer, "Segment Routing
Architecture", draft-filsfils-rtgwg-segment-routing-00.txt
(work in progress), June 2013.
[SR-PCEP] Sivabalan, S., Filsfils, C., Medved, J., Crabbe, E., and
R. Raszuk, "PCEP Extensions for Segment Routing", draft-
sivabalan-pce-segment-routing-00.txt (work in progress),
June 2013.
8.2. Informative References
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
Authors' Addresses
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
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Jan Medved
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
USA
Email: jmedved@cisco.com
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